Cancrinite is a well-known natural zeolite having a SiO.sub.2 :Al.sub.2 O.sub.3 ratio of two which is readily synthesized in systems consisting of Na.sub.2 O-SiO.sub.2 -Al.sub.2 O.sub.3 -H.sub.2 O in the presence of a large variety of salts. See, for example, Barrer et al., J. Chem. Soc. A, 1523 (1970). In addition, U.S. Pat. No. 3,433,736 discloses hydroxyparacancrinite of the formula 3(Al.sub.2 O.sub.3, 2SiO.sub.2, Na.sub.2 O)2NaOH from a mixture of silica, aluminum hydroxide and water. The main characterizing feature of cancrinite is a single 12-ring channel parallel to the `c` axis as described by Jarchow, Zeit Krist., 122, 407 (1965) and Pahor et al., Acta Cryst., B38, 893 (1982)). Because this channel is invariably faulted or blocked by salt molecules, the structure tends to have very poor sorption properties, even when attempts are made to remove the excess salt molecules. See Barrer and Vaughan, J. Phys. Chem. Solids, 32, 731 (1971). The synthesis chemistry has been reviewed at great length by Barrer, Hydrothermal Chemistry of Zeolites, Academic Press (1982), Ch. 7.
If the channel of the cancrinite could be unblocked, the cancrinite would be expected to be a highly active catalyst (as are other zeolites having 12-ring channel systems) such as mordenite and offretite for cracking, hydrocracking and hydrodewaxing, and mordenite and zeolite L for hydroisomerization.
U.S. Pat. No. 3,459,501 teaches preparation of a zeolite by treating a silica-alumina gel with aqueous ammonia and then reacting the treated gel with sodium hydroxide and aluminum sulfate. The zeolite prepared is a high-silica faujasite, not a cancrinite.
Although the synthetic analog of the zeolite cancrinite is easy to produce and is otherwise well-characterized, it always has an Si/Al ratio at unity, whether in its natural state or synthesized in a wide variety of systems.